The present invention relates to a method and a device for precipitating a beverage sediment such as used in beverage production machines.
Beverage production machines, such as coffee machines and also e.g. beverage vending machines, which do not process instant powders, are often provided with a cleaning device for rinsing out beverage residues, such as coffee or tea sediments, after each brewing operation. When the rinsed-out residues, such as the exhausted coffee sediment or the exhausted tea leaves, have to be removed from the rinsing liquid, such beverage production machines are normally equipped with a sediment receptacle of the type described e.g. in German Utility Model 91 09 901. Such sediment receptacles have filtering walls through which the filtrate, i.e. the cleaning liquid, can flow off, whereas the beverage sediment remains in the receptacle, where it is collected and from which it can finally be removed and disposed of. In order to reduce the maintenance work, these sediment receptacles are normally large enough for collecting the beverage sediment of at least a plurality of brewing operations. The beverage-sediment filter cake accumulating in the sediment receptacle will therefore become thicker and thicker whereby the filtering process will be slowed down. In addition, it turned out that a sedimentation in the filter cake takes place over a period of repeated cleaning processes, i.e. the finer particles, especially particles of coffee sediment, will accumulate on the surface of the filter cake and slow down the flow through said filter cake to a disproportionally high extent. In extreme cases, it may happen that no filtrate at all flows off and that the sediment receptacle overflows if servicing is delayed for only a short period of time.
Hence, it is the object of the present invention to provide a device and a method for precipitating beverage sediment from the rinsing mixture of beverage production machines, said device being designed in a structurally simple manner such that it can be serviced more easily.
It turned out that the residence time of the rinsing mixture in the sediment receptacle can be reduced substantially, when the rinsing mixture is filtered in two steps, i.e. when a first sub-amount of filtrate is initially removed from the rinsing mixture in a first filter and when the residual rinsing mixture is then passed through a second filter by means of which the residual, thus concentrated filtrate is precipitated. It turned out that this two-step filtrate precipitation has the effect that, on the one hand, the sedimentation and, consequently, the formation of a blocking layer on the surface of the beverage sediment is avoided and that, on the other hand, the remaining beverage-sediment filter cake is much drier than in the case of the known, one-step precipitation.
It will, for example, be particularly advantageous when the passage opening of the flow connection is provided directly on the first filter.
The rinsing mixture is simultaneously used as a rinsing agent for the first filter, which entrains the filter cake that has accumulated on said first filter, so that said first filter will always remain free.
This rising effect can be improved in cases in which the first filter is implemented as a screen filter when the rinsing conduit terminates in an expedient mode of arrangement with respect to said screen filter.
Instead of a screen filter, it is also possible to use a tubular filter for said first filter; there is also a particularly preferred structural design of a tubular filter.
There is a specially preferred structural design of the second filter.
Finally, an additional cleaning device for said first filter can be provided, said cleaning device preventing clogging of said first filter even in the case of comparatively long off-times.